Hearing aids today are typically manufactured in one piece—i.e. one component comprising all necessary sub-devices such as microphone, amplifier and receiver—the latter being used to generate a sound pressure so as to excite the eardrum in response to sound pressure captured by the microphone. The components—microphone, amplifier and receiver—are encapsulated in a common plastic shell as illustrated in FIG. 1.
As seen in FIG. 1, the hearing aid is positioned at a relatively large distance from the eardrum—in front of the bony area of the ear canal. The reason for this being that the plastic material forming the shell encapsulating the above-mentioned components is hard, which makes it impossible to position a conventional hearing aid with a plastic shell in the bony area of the ear canal without introducing pain to the user of the hearing aid.
Another disadvantage of one-piece hearing aids is the large distance between the receiver output and the eardrum to be excited.
Other disadvantages relating to one-piece hearing aid are acoustic feedback from the receiver to the microphone, vibrations of the receiver, which is transmitted to the ear canal, unpleasant for the user and finally the rather complicated and painful mounting of the hearing aid.
U.S. Pat. No. 6,094,494 discloses a device and a method for fitting a sound transmission device to provide an easy and effective fit, reduce feedback, and improve user comfort comprises an ear-piece component having a face at one end with operative components and a stem adjacent the other end. The stem houses a speaker tube which protrudes from the component, and it has a retaining means for securing an inflatable, resilient fitting balloon thereon. The balloon has a sound transmission duct within it which can be coupled to the speaker tube so that when the balloon is secured to the stem, a continuous path is provided for the transmission of sound from the component to the user's ear canal external the balloon. This assembly (e.g., the component and attached balloon) is inserted into the ear canal when the balloon is in a deflated configuration. Air is then pumped into the balloon, e.g., through an air channel in the ear-piece component, to inflate the fitting balloon. The inflated fitting balloon engages the ear-piece component against the walls of the user's ear canal and prevents sound from travelling to the external ear and face of the component.
U.S. Pat. No. 4,133,984 discloses a plug-type hearing device comprising a sound-leading portion being inserted into the auditory miatus, a first envelope attached around the sound-leading portion, a second envelope being positioned at the outside of the auditory miatus and being communicated with the first envelope through a pipe, and a holding means for holding an expanded state of the first envelope when the volume of the latter is increased, wherein the volume of the second envelope is decreased to increase the volume of the first envelope by the pressure of a fluid contained inside, and the expanded first envelope is closely contacted with the wall surface of the auditory miatus.
However, the balloon introduced in U.S. Pat. Nos. 6,094,494 and 4,133,984 does not solve the above-mentioned problems in that the hearing aid is still a one-piece device—the only difference compared to the hearing aid of FIG. 1 is that a flexible sound-leading portion has been attached to the hearing aid in order to guide sound from the receiver, which is still positioned at a large distance from the eardrum, to an opening near the inner end of the flexible sound-leading portion.
Thus, problems related to the large distance between the receiver output and the eardrum is not solved by the set-ups suggested in U.S. Pat. No. 6,094,494 and 4,133,984. Even further, since the systems of U.S. Pat. No. 6,094,494 and 4,133,984 are still one-piece hearing aids problems such as acoustic feedback from the receiver to the microphone, vibrations of the receiver, which is transmitted to the ear canal, are still present and may easily influence the performance of the hearing aid in a negative direction.
It is an object of the present invention to provide an external receiver module, which solves the above-mentioned problems. The external receiver module according to the present invention has the following advantages:                The receiver may be brought close to the eardrum (in the bony area).        Using an expansible, preferably inflatable, medium to keep the receiver in its place instead of a plastic shell.        Dividing the conventional one-piece hearing aid into two parts connected by a tube.        That part of the hearing aid comprising the microphone may be removed—e.g. for repair—without removing the receiver module from the ear canal.        No problem with cerumen.        No acoustic feedback to the microphone.        No occlusion effect.        The expansible medium may be expanded to the user's wishes (comfort).        Easy to fit in the ear.        The expansible medium is soft which is of importance in the bony area.        No vibration transfers from the receiver to the ear canal.        The receiver module including the expansible medium may be removed and cleaned without surgery by the audiologist.        